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# Tag Archives: body

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## If gravitation suddenly stops?!

If gravitation suddenly stops …… neglecting the rotation … if someone is standing on ground ….. will the normal reaction disappear?? If yes why? I want to know when does normal reaction acts on a body? and in the absence of weight why would it disappear?

(Ahwan Abhinandan Joshi asks)

## Kinetic Energy – Numerical Problem

a running man has half the kinetic energy that a boy of half his mass has.the man speed up by 1m/s and then has the same kinetic energy as the body. what were the original speeds of man and boy?

## What is Eddy Current?

Eddy currents are circulating currents induced in the body of a solid conductor whenever the magnetic flux linked with it changes. It is called EDDY CURRENT because they are like eddies formed in water.

## Class XI CBSE – Revision Questions MCQ – Semester 1

1. What is the gravitational field strength of a planet when the weight of a 100 kg astronaut is 400 N?

a)      ¼ N kg-1   b) 9.8 N kg-1 c) 4 N kg-1  d) infinity

1. The only natural satellite of the earth complete orbits in about

a)      24 days b) 27.3 days c) 30 days d) 365 1/4 days

1. The satellite that revolves in a polar orbit is called

a) Natural Satellite b) Geostationary satellite   c) Polar Satellite   d) None of these

4)  The height of a communication satellite above the earth’s surface is about

a) 1km b) 100 Km    c) 10,000 Km    D) 36000 Km

5) At what depth below the earth’s surface does the weight of  a body  becomes 1% of its value at the surface of the earth?

a) 32Km  b) 64 Km   c) 128 Km   d) 164 Km

6) The arte of change of angular momentum is called

a) a Force  b) Torque  c) Impulse  d) None of these

7) Which of the following has the largest moment of inertia (Each object has same mass)

a) Solid sphere

b) Bar Magnet

c) Ring about an axis perpendicular to its plane

d) Disc about an axis perpendicular to its plane

8) A hollow cylinder and a solid cylinder having same mass and same diameter are related simultaneously from rest from the top of the inclined plane. Which of them will reach the bottom first?

a) Solid cylinder

b) Hollow Cylinder

c) Both will reach the bottom together

d) One having greater density

9) A body moving with a constant speed on a horizontal surface does not have

a) Velocity

b) Momentum

c) Kinetic Energy

d) Acceleration

10) Which of the following has its unit as Newton-Second

a) Torque b) Momentum   c) Energy   d) Planck is constant

FIND MORE HERE http://www.scribd.com/doc/7067782/MCQ-on-Basic-Physics

## Horizontal projectile and freely falling body

A rifle at a height H aimed horizontally fires a bullet to the ground. At the same time , a bullet with the same mass in dropped from the same height. Neglecting air resistance, which one hits the ground first?Explain.
ED posted
Answer:
Both will hit the ground simultaneously.
When a body is projected horizontally, its initial vertical velocity […]

## What is twin paradox?

TWIN PARADOX is a paradoxical situation coming in while explaining the theory of relativity. “Time dilation” is one of the important consequences of relativity. It says that if a body is moving with relativistic speeds, time will dialate for it. That is, a duration of 1 second for him will be more than that for a person […]

## A body is dropped from a tower of height 96 m. Another body is thrown up from the ground after a second with a velocity of 40 m/s.When and where they will meet?

A body is dropped from a tower of height 96 m. Another body is thrown up from the ground after a second with a velocity of 40 m/s. When and where they will meet?
SOUNDARYA asked
Answer:
For the first body,
u=0 m/s
Let S=x (from top)
x=0.5 gt2  ————— (1)
For the second body,
u=40 m/s
a=-g
S=96-x
96-x=40 t -0.5 gt2 ———–(2)
(1) + (2) =>
96=40t
or
t=96/40 = 2.4 […]